fix(plugin): add timeout protection to getClient() in before_prompt_build hook

[Meskjei]

Problem

The before_prompt_build hook calls await getClient() without timeout protection. If the OpenViking client hasn't finished initializing when the hook is triggered, the agent will hang indefinitely waiting for the client Promise to resolve.

This happens because:

1. Plugin loads and registers the before_prompt_build hook
2. User sends a message before start() function completes OpenViking server startup
3. Hook triggers and calls await getClient()
4. getClient() waits for clientPromise to resolve
5. But clientPromise only resolves after start() finishes starting the OpenViking service
6. Deadlock: hook blocks agent → agent can't complete → start() can't finish

Solution

Wrap getClient() call with withTimeout() (5 seconds):

• If client initializes in time, proceed normally with memory recall
• If timeout, log warning and skip recall gracefully
• Agent continues without blocking

Testing

Tested locally with OpenClaw + OpenViking plugin:

• Before fix: Agent hangs on first message if OpenViking service not ready
• After fix: Agent responds normally, recall skipped gracefully if timeout

Related Issues

• Similar to [Bug]: memory-openviking plugin before_agent_start auto-recall hangs indefinitely, causing total silent agent failure #673 (which fixed auto-recall timeout but not the initial getClient() call in hook)
• Addresses [Bug]: examples/openclaw-plugin/index.ts missing withTimeout protection (same as #673) #748 (directory refactor bug where timeout fix wasn't synchronized to new plugin location)